1. Field of the Invention
This invention relates to an apparatus for supplying a resin material to a molding die by weighing and agitating in the process of plastic encapsulation molding of electronic parts, etc, and to a method thereof.
2. Description of the Related Art
Conventionally, an apparatus illustrated in FIG. 5 is extensively used as the one of this type.
A molding die 61 for forming a plastic encapsulation mechanism shown in FIG. 5 is configured in such a way that a top mold half 61A and a bottom mold half 61B are provided removably, and these top and bottom mold halves 61A and 61B are provided with multiple cavities 63 engraved therein. Multiple mold pots 62 are provided among the cavities of the bottom mold half 61B, and these pots 62 are communicated to cavities 63 through runners 64 and gates 65.
Accordingly, when tablets 72 as resin material are put in the mold pots 62 of the molding die 61 heated and held at a high temperature, and plungers 67 fitted slidably in the mold pots 62 are operated to move up toward the top mold half 61A as indicated by the arrow, then the tablets 72 are pressed and are molten as they are heated by the molding die 61. They are then charged via the runners 64 and gates 65 into the cavities 63 provided with lead frames 63a connected with electronic parts or the like in advance, and plastic encapsulation is carried out in this mechanism.
However, a resin material according to the aforementioned prior art plastic encapsulation is used in the form of tablets 72. This makes it necessary to store many types of the tablets 72 each having a sizes conforming to the capacity of the cavities 63 of the molding die 61 when manufacturing various types of moldings.
Furthermore, the corner portion in particular is damaged during transportation and storage of the tablets 72, and the weight is reduced. This results in a short-shot accompanied by non-performing products. This requires tablets 72 to be managed by separation of damaged ones or a similar method.
Thus, an object of the present invention is to provide a resin material supply apparatus and method which will ensure a predetermined amount of resin material to be supplied and the molding quality to be improved, without the need for storing many types of tablets or managing the products by separation of damaged ones or by other methods.
To attain the above object, a first embodiment of the present invention provides a resin material supply apparatus comprises a weighing unit, an agitating unit, a traveling unit, and a supply unit.
The weighing unit allows a predetermined amount of the aforementioned resin materials to be loaded into each of weighing pots arranged below via weighing means which has a screw inserted in the weighing tube on the bottom of a hopper storing resin materials,
The agitating unit permits agitation to be performed by the rotation of each of plungers with an agitating rod protruded from the tip via agitating means having the aforementioned plungers inserted in multiple agitating cups where the aforementioned resin materials are exchanged between the aforementioned weighing pots and the aforementioned multiple agitating cups arranged in parallel with these pots,
The traveling unit allows the aforementioned agitating unit to travel in the forward and backward direction in the space between the aforementioned weighing unit and the molding die via traveling means provided with a pulley and belt mounted on the shaft of a motor capable of forward/reverse drive.
The supply unit permits the resin material in agitating cups to be extruded into the mold pot of the molding die by means of the aforementioned plungers via vertical traveling means provided with a pulley and belt mounted on the shaft of a motor capable of forward/reverse drive.
Thus, the first embodiment of the present invention has the effect of eliminating the need for using resin materials having been weighed and formed into tablets in advance, because the resin material is weighed, agitated and molten, and is supplied to the molding die.
It should be noted that the resin material can be exemplified by a molding material for encapsulation of electronic parts by plastic molding. Thermosetting epoxy resin is a common material.
The molding material frequently used in the prevent invention is powdery or granular, and is characterized by the grade where the temperature of the agitating cups is kept at about 120 degrees Celsius to melt the material, and the molding die temperature is kept at about 180 degrees Celsius to set it.
A second embodiment of the present invention provides a resin material supply apparatus according to the first embodiment further characterized in that;
the aforementioned weighing means comprises a screw for forming a weighing unit, wherein the aforementioned screw is mounted vertically inside the hopper to lead to the bottom end of the weighing tube on the bottom of the hopper and is connected to a weighing motor, and
a pot unit movable in the forward and reverse directions is provided on the bottom end of the aforementioned weighing tube, wherein a weighing pot equipped with a shutter plate opened and closed by sliding on the underside is arranged.
Thus, the second embodiment of the present invention has the effect of eliminating a defect or variation in weight which may occur to the tablets (resin materials) formed in advance, and hence removing the need for tablet management by separation or the like, because a screw is inserted into the weighing cylinder for rotation, and a predetermined amount of the resin material can be weighed and loaded into the weighing pot.
A third embodiment of the present invention provides a resin material supply apparatus according to the first embodiment further characterized by the aforementioned agitating means, wherein
agitating cups are moved by the pulley and belt mounted on the shaft of the cup traveling motor to the bottom of the weighing pot moved by a weighing pot traveling cylinder so that the aforementioned resin material is received;
the aforementioned multiple agitating cups are moved to the bottom of the aforementioned plunger mounted on the bottom linking plate installed on a guide post;
an agitating rod is protruded from the tip of the plunger by the action of an agitating cylinder mounted on the bottom linking plate; and
gears mounted on the aforementioned plungers are meshed with each other by the action of the agitating motor with gears mounted on the shaft thereof so that the aforementioned plungers are rotated,
thereby allowing the aforementioned resin material inside the agitating cup to be agitated.
Thus, the third embodiment of the present invention has the effect of ensuring homogenized agitation and melting at a high speed because the resin material received in the agitating cup can be agitated by the rotation of a protruded plunger.
A fourth embodiment of the present invention provides a resin material supply apparatus according to the first embodiment further characterized by the aforementioned traveling means, wherein
a traveling motor is installed on the stay extending downwardly of multiple rails along which a running cart with the agitating unit mounted therein travels, and
the aforementioned running cart engaged with the belt can be moved in the forward and reverse directions in the space from the aforementioned weighing unit to the aforementioned molding die by the forward and reverse drive of the traveling motor via the pulley and belt mounted on the shaft of this motor.
Thus, the fourth embodiment of the present invention has the effect of ensuring direct transmission of the forward and reverse drive of the motor and hence high-speed traveling and accurate positioning in traveling, because the agitating unit mounted on the running cart is engaged with the belt.
A fifth embodiment of the present invention provides a resin material supply apparatus according to the first embodiment further characterized by the aforementioned vertical traveling means, wherein
ball screws are arranged in parallel with one another among the aforementioned multiple guide posts installed on the aforementioned agitating unit;
these ball screws are meshed with ball screw nuts;
the aforementioned multiple plungers installed in a row on the bottom linking plate mounted on these screw nuts are moved downward via the pulley and belt mounted on the shaft of the vertical traveling motor; and
a shutter plate provided on the bottom surface of the agitating cup so as to be opened or closed through sliding is made to slide and open, whereby the molten resin material from the agitating cup is supplied to the mold pot of the aforementioned molding die.
Thus, the fifth embodiment of the present invention has the effect of ensuring powerful, accurate and simultaneous lowering of the bottom linking plate where multiple plungers are mounted in a row, because a ball screw mechanism linked to a vertical traveling motor is used.
A sixth embodiment of the present invention provides a resin material supply apparatus according to the first to fifth embodiments further characterized in that the aforementioned resin material is powdery or granular.
Thus, the sixth embodiment of the present invention has the effect of reducing the material cost because the resin material is powdery or granular.
A seventh embodiment of the present invention provides a resin material supply method comprising;
a weighing step of weighing resin materials stored in a hopper and loading it into a weighing pot,
an agitating step of feeding the aforementioned weighed resin materials into multiple agitating cups, and agitating and melting them via an agitating unit,
a traveling step of moving the agitating unit in the forward and reverse directions in the space from the weighing pot area to the molding die, and
a supply step of extruding and supplying the aforementioned resin materials molten in the agitating cup into the pot of the aforementioned molding die;
wherein the aforementioned resin material supply method is capable of weighing, agitating and molding a predetermined amount of resin materials even when these materials are powdery or granular.
Thus, the seventh embodiment of the present invention has the effect of eliminating the need of storing and managing many types of tablets and checking possible damages or managing weight, thereby cutting down management expenses. This is because the resin material can be powdery or granular; it is not required to have been formed in a tablet.